caisson disease vs illness

caisson disease and illness both are nouns.

Word	Noun	Adjective	Verb	Adverb
caisson disease	Yes	No	No	No
illness	Yes	No	No	No

As nouns, illness is a hypernym of caisson disease; that is, illness is a word with a broader meaning than caisson disease:

caisson disease: pain resulting from rapid change in pressure
illness: impairment of normal physiological function affecting part or all of an organism

Other hypernyms of caisson disease include malady, sickness, unwellness.

caisson disease (noun)	illness (noun)
pain resulting from rapid change in pressure	impairment of normal physiological function affecting part or all of an organism